Patent US 3,988,577

The invention comprises apparatus and methods for controlling and monitoring most of the energy systems used by man. An energy level to be maintained is predetermined and electronically established as a time interval. Sensing means are exposed to the actual energy level for influencing the parameter value of the sensing means in accordance with the sensed energy level. The parameter value is converted to a digital pulse train with the time period between pulses being proportional to the parameter value being sensed. A reference or standard time base is generated, from which a measure of time for the period is obtained. This measure of time is compared against the time interval to determine if energy need be applied to reach the predetermined energy level, if alarm is required and to display a digital or numerical representation of the actual energy level.